1. Field of the Invention
The present invention relates to a liquid application mechanism and an inkjet printing apparatus including the liquid application mechanism.
2. Description of the Related Art
There is known a system such as a spin coater, a roll coater, a bar coater or a die coater as an application mechanism for coating a medium with a liquid or a liquid material. In the field of inkjet printing apparatuses, there is proposed an inkjet printing apparatus with an application mechanism for in advance applying a reaction liquid on a print medium to improve a print concentration or reduce bleeding thereon.
For example, Japanese Patent Laid-Open No. 2002-96452 has proposed an application mechanism in which a rotational operation of a coating roller is performed for each given time during a stand-by condition, thus preventing a coating liquid attached on the coating roller from being solidified. In addition, Japanese Patent Laid-Open No. 2007-44650 has disclosed an application mechanism in which a roller is rotated to supply a coating liquid from a retaining member of the coating liquid to a peripheral surface of the roller, and a liquid reservoir is formed in a contacting portion between the roller and the retaining member of the coating liquid by performing a rotational operation of the roller before performing an application operation thereof. By in advance forming the liquid reservoir of the coating liquid in the contacting portion between the roller and the retaining member of the coating liquid in this way, the coating liquid acts as a lubricant, reducing wear of the roller generated at the time a part of the peripheral surface of the roller is in contact with the retaining member of the coating liquid.
However, in a case where the rotational operation of the coating roller is designed to be performed for each given time during the stand-by condition of the application mechanism as disclosed in Japanese Patent Laid-Open No. 2002-96452, even if the application mechanism is left in a state where the power of the application mechanism is OFF, it is required to perform rotation of the coating roller for each given time. Accordingly, since the rotational operation of the coating roller is performed for each given time even in a case where the power of the application mechanism is OFF, separate recovery means such as a built-in power source is required in the application mechanism. In consequence, a structure of the apparatus is complicated, leading to an increase in manufacturing cost of the apparatus. In addition, Japanese Patent Laid-Open No. 2002-96452 describes a technology in which the coating roller is operated to be dipped in the coating liquid as an initial process of the application operation or the coating roller is operated to be separated away from a counter roller at the stand-by time of the coating roller. However, even if the application mechanism is assumed to perform such an operation, it is difficult to remove the liquid attached on the coating roller after the previous application operation is completed. Therefore, at the time of performing the next application operation, it is required to remove the solidified coating liquid left on the coating roller.
Further, as disclosed in Japanese Patent Laid-Open No. 2007-44650, in regard to the method of taking a measure against the wear of the roller by in advance forming the liquid reservoir in the contacting portion between the roller and the retaining member, it is difficult to adjust an amount of the coating liquid forming the liquid reservoir. Therefore, there is a possibility that the coating liquid is collected in the retaining member due to a negative pressure inside the retaining member. Therefore, there are some cases where it is difficult to in advance form the liquid reservoir having an amount of the coating liquid effective for reducing the wear of the roller in the periphery of the contacting portion between the roller and the retaining member.